This invention relates to an optical printer head, and more particularly to an optical printer head adapted to carry out absorption and transmission of light emitted from a light source through a filter and reflection of the light through a lens, to thereby irradiate it on a photosensitive medium while focusing it thereon, resulting in forming a desired image on the photosensitive medium.
A conventional optical printer adapted to form a desired image on a record medium such as a photosensitive film or the like typically includes a fluorescent luminous tube which is used as a light source. The optical printer is so constructed that light emitted from the fluorescent luminous tube is guided through red, green or blue filters arranged so as to be selectively changeable with each other, to thereby obtain light of the three primary colors, which is then irradiated for writing on a record medium such as a color film or the like, resulting in a full-color image being formed on the record medium.
Now, such a conventional optical printer head will be described with reference to FIGS. 7 to 9, wherein FIG. 7 is an exploded perspective view of the optical printer head and FIGS. 8 and 9 each are a side elevation view in section of the optical printer head. The printer head generally designated at reference numeral 100 includes a fluorescent luminous tube 101 including a plurality of luminous dots for emitting linear light and acting as a light source. Also, it includes a filter holder 102 for holding red, green and blue color filters R, G and B thereon. The thus-constructed fluorescent luminous tube 101 and filter holder 102 are housed or received in a housing 103. Also, the optical printer head 100 includes a selfoc lens array 104 arranged above the housing 103 for forming incident light into an erected real image at an equi-magnification.
The housing 103, as shown in FIG. 8, is formed with an inner space in which the fluorescent luminous tube 101 and filter holder 102 are arranged. The housing 103 is mounted thereon with a bottom plate 106 to close an opening 105 of the space while receiving the fluorescent luminous tube 101 and filter holder 102 in the space. The housing 103 and bottom plate 106 cooperate with each other to provide a box-like base 107. The filter holder 102 is formed thereon with elongated filter holding holes 108 in a manner to extend in a direction perpendicular to a sub-scanning direction indicated at an arrow A in FIG. 8 in which the optical printer head 100 is moved. The color filters R, G and B are held in the filter holding holes 108, respectively.
The fluorescent luminous tube 101 includes a glass plate 101a. The filter holder 102 is slid along an upper surface of the glass plate 101a and a wall surface of the opening 105 in the direction A or sub-scanning direction, resulting in selective change-over among red, green and blue colors being carried out. The selfoc lens array 104 is formed by constructing a plurality of selfoc lenses into a single module.
However, the optical printer head 100 thus constructed, as shown in FIG. 9, causes an end of the upper surface of the glass plate 101a of the fluorescent luminous tube 101 to tend to be caught in the filter holding holes 108 in which the color filters R, G and B are held, when the filter holder 102 is slid in the sub-scanning direction A in FIG. 8 to carry out selective change-over among the color filters R, G and B.
When the filter holder 102 is slid under such circumstances, the filter holder 012 made of a resin material is shaved off to produce shavings or dust. When the thus-produced dust adheres to a surface of the color filters R, G and B, light emitted from the fluorescent luminous tube 101 is kept from satisfactorily permeating through the filters, to thereby fail to permit light to appropriately form an image on a photosensitive film W, leading to a deterioration in quality of the image.
Also, replacement of the fluorescent luminous tube 101 of which a life expired requires to detach the bottom plate 106 from the housing 103, to thereby cause the color filters R, G and B to be exposed to an ambient atmosphere. Such exposure causes dust in an ambient atmosphere to adhere to the color filters R, G and B, resulting in the image quality being further deteriorated.
Referring now to FIG. 10, another conventional optical printer head is illustrated, which is generally designated at reference numeral 110. In FIG. 10, reference characters like those in FIGS. 7 to 9 designate corresponding parts. The optical printer head 110 includes a selfoc lens array 104 arranged in a through-hole 111a formed via a central portion of a body 111. The body 111 is provided on a lower portion thereof with a flat section 111b, which cooperates with a frame 112 to constitute a housing 113. The selfoc lens array 104 is arranged in a manner to extend through the though-hole 111a into the housing 113. The housing 113 has the selfoc lens array 104 and a filter holder 102 received therein while keeping a distal end or outgoing surface 104a of the selfoc lens array 104 and one surface of the filter holder 102 facing each other.
The housing 113 is formed with an opening 114, on which a bottom plate 106 is mounted, to thereby provide a box-like base 115. The bottom plate 106 is so arranged that an inner surface 106a thereof is opposite to the other surface 102b of the filter holder 102. The bottom plate 106 is formed with a hole 106b in correspondence to the distal end 104a of the selfoc lens array 104. The body 111 is provided at an upper portion thereof with a flange 111c formed therein with a hollow section 111d. The hollow section 111d has a flat surface 111e, which is mounted thereon with a fluorescent luminous tube 101 while keeping a glass plate 101a abutted thereagainst.
In the thus-constructed optical printer head 110, the filter holder 102 is slid to select any desired one of color filters R, G and B to drive the fluorescent luminous tube 101. In FIG. 10, the color filter G is selected by way of example. Driving of the fluorescent luminous tube 101 permits it to emit light, which is guided through the hollow section 111d, to thereby be collected on an incident surface 104b of the selfoc lens array 104. The light thus collected is then discharged through the outgoing surface 104a of the selfoc lens array 104 and partially absorbed by the color filter G. Light permeating through the color filter G is guided through the hole 106b of the bottom plate 106 to a photosensitive plate W, to thereby form an image thereon.
Unfortunately, the optical printer head 110 thus constructed causes the outgoing surface 104a of the selfoc lens array 104 to tend to be caught in filter holding holes 108 in which the color filters R, G and B are held, when the filter holder 102 is slid in a sub-scanning direction A to carry out selective change-over among the color filters R, G and B.
When the filter holder 102 is slid in such a state, the filter holder 102 made of a resin material is shaved off to produce shavings or dust. When the thus-produced dust adheres to a surface of the color filters R, G and B, light emitted from the fluorescent luminous tube 101 is kept from satisfactorily permeating through the filters, to thereby fail to permit light to appropriately form an image on the photosensitive film W, leading to a deterioration in quality of the image as in the optical printer head 100 described above with reference to FIGS. 7 to 9.
In addition, when it is desired to clear the outgoing surface 104a of the selfoc lens array 104 for maintenance, it is required to detach the bottom plate from the housing 113, to thereby cause the color filters R, G and B to be exposed to an ambient atmosphere. This causes dust in an ambient atmosphere to adhere to the color filters R, G and B, resulting in the image quality being further deteriorated, as in the optical printer head 100 described above.